ACY-1215 induces dose-dependent cytotoxicity in MM cells. (A) ACY-1215 decreases MM-cell viability in a dose-dependent manner. Cells were treated with increasing doses of ACY-1215 (0-8μM) for 48 hours, and cell viability was measured by MTT assay (left panel). ANBL-6.BR cells were treated with increasing doses of ACY-1215 (0.4μM) and bortezomib (0-5nM) to show their bortezomib resistance for 48 hours; cell viability was measured by MTT assay (right panel). (B) CD138⁺ patient MM cells (patients 1-4) were similarly tested in cytotoxicity assays (MTT) at 48 hours. (C) MM.1S cells were cultured for 48 hours with ACY-1215 (0-4μM) in the presence or absence of BMSCs (left) and in the presence or absence of IL-6 (10 ng/mL) and IGF-1 (50 ng/mL). ³H-thymidine incorporation was measured during the last 8 hours of incubation to measure DNA synthesis.